1. Field of the Invention
The present invention is in the field of nondestructive testing utilizing the penetrant inspection technique, and provides an improved penetrant composition in the form of a crayon and a remover in the form of a crayon, both being adapted for use of the penetrant inspection technique at elevated temperatures.
2. Description of the Prior Art
The standard penetrant inspection technique has been highly developed for many decades. Basically, the technique consists in first cleaning the workpiece to be inspected to remove surface films and oxides and then flooding the area to be inspected with a penetrant composition. Such composition for normal use consists of a light hydrocarbon oil or an emulsifiable oil containing either a visible penetrant, usually a red dye, or a fluorescent dye. The penetrant is allowed to dwell on the surface of the workpiece for a sufficient time to enable it to seep into surface discontinuities or flaws which extend to the surface. The excess penetrant is then removed by wiping, or emulsification in the case of a hydrocarbon oil, or by washing with water in the case of an emulsifiable penetrant composition. After drying, a developer is applied to the surface which may take the form of finely divided solid particles or a dispersion of solid particles in a liquid or an aerosol. The deposit of finely divided particles serves to immobilize the penetrant being exuded from the flaw and to render the penetrant contrastingly visible to the power deposit. Inspection of the piece is then done under ordinary white light in the case of a visible penetrant or under ultraviolet irradiation when using the more sensitive fluorescent dyes.
The penetrant inspection technique has become a mainstay of American industry. It does have some limitations, however, particularly with respect to temperature limitations. Both visible and fluorescent dye materials lose their brilliance and in some cases their characteristic color completely when operating at temperatures in excess of about 200.degree. F. (93.degree. C.). Yet, it would be highly desirable to use this type of inspection on metal shapes in the rolling mill, or newly welded workpieces which are at a temperature substantially in excess of the prior limiting temperature.